diff --git a/E04_Stab3D/logic/E04_Stab3D_Mesh.ts b/E04_Stab3D/logic/E04_Stab3D_Mesh.ts
index 84ac09770..b334d60f9 100644
--- a/E04_Stab3D/logic/E04_Stab3D_Mesh.ts
+++ b/E04_Stab3D/logic/E04_Stab3D_Mesh.ts
@@ -84,9 +84,10 @@ export function cutCells(
     const x = grid.x0 + (index % grid.nx) * grid.dx;
     const y = grid.y0 + Math.floor(index / grid.nx) * grid.dx;
     const slip = slipHeight(best, x, y);
-    if (slip === null) return;
-    const base = Math.max(slip, floor.get(index) ?? -Infinity);
-    if (base < top) out.set(index, base);
+    const base = Math.max(slip ?? top, floor.get(index) ?? -Infinity);
+    // 엔진 덩이 셀 = 그대로(셀 안 일부만 잘린 가장자리 = 두께 0) · 옛 저장본 = 셀 중심이 잘린 칸만
+    if (mass) out.set(index, Math.min(base, top));
+    else if (base < top) out.set(index, base);
   });
   return out;
 }
diff --git a/resources/tester/test_533_3_e04_logic.py b/resources/tester/test_533_3_e04_logic.py
index b085d08f0..d323e7f1d 100644
--- a/resources/tester/test_533_3_e04_logic.py
+++ b/resources/tester/test_533_3_e04_logic.py
@@ -64,6 +64,7 @@ writeFileSync(process.argv[3], JSON.stringify({
   ellipsoid: mesh(M.slipMesh(c.grid, c.z, c.ellipsoid)),
   cut: Array.from(M.cutCells(c.grid, c.z, c.sphere).keys()),
   massCut: Array.from(M.cutCells(c.grid, c.z, { ...c.sphere, cells: [7 * 21 + 10, 7 * 21 + 11, 0] }).keys()),
+  massBase0: M.cutCells(c.grid, c.z, { ...c.sphere, cells: [0] }).get(0),
   center: M.footprintCenter(c.grid, M.cutCells(c.grid, c.z, c.sphere), c.sphere),
   centerEmpty: M.footprintCenter(c.grid, new Map(), c.sphere),
   floored: Object.fromEntries(M.cutCells(c.grid, c.z,
@@ -208,7 +209,8 @@ def test_terrain_hole_matches_cut(ts):
     """활동체를 걷어낸 지표 = 지표 꼭짓점 − 잘린 셀 · 구멍 테두리는 활동면 메쉬와 같은 꼭짓점."""
     cut = [i for i, _ in _py_cut(SPHERE)]
     assert ts["cut"] == cut
-    assert ts["massCut"] == [7 * 21 + 10, 7 * 21 + 11]  # 엔진 덩이 셀만 · 안 잘린 셀(0)은 빠짐
+    assert ts["massCut"] == [0, 7 * 21 + 10, 7 * 21 + 11]  # 엔진 덩이 셀 그대로(0 = 안 잘림 · 두께 0)
+    assert ts["massBase0"] == Z[0]
     assert ts["holed"]["n"] == ts["terrain"]["n"] - len(cut)
     assert not set(ts["holed"]["cells"]) & set(cut)
     assert _py_rim(set(cut)) <= set(ts["holed"]["cells"])